Title:
Magneto-optical information storage unit
United States Patent 3059538


Abstract:
An information storage unit (see Group XIX), comprises a film of magnetically polarized crystalline material so prepared as to contain an operative area throughout which the crystals are magnetically orientated in the same direction, the material being such that it rotates the plane of polarization of light in one direction or the other according to whether or not the magnetic polarity has been reversed. As described, the film comprises an intermetallic compound of manganese and bismuth supported on a glass plate. The film is prepared by first depositing on the plate by vacuum evaporation a layer of manganese, similarly depositing a layer of bismuth, and then heating the layers in vacuo up to 300 DEG C. to form the crystalline compound. Finally the film is uniformly magnetized, in a direction normal to its surface, by an electromagnet applying a field of the order of 3,000 oersteds. It is stated that a film having a thickness of 1,000 Augstrom units transmits 20% of the incident light and rotates the plane of polarization through an angle of 5 degrees. Specification 789,660 is referred to.



Inventors:
Sherwood, Richard C.
Williams, Howell J.
Application Number:
US66515657A
Publication Date:
10/23/1962
Filing Date:
06/12/1957
Assignee:
BELL TELEPHONE LABOR INC
Primary Class:
Other Classes:
347/111, 359/283, 359/324, 360/59, 360/131, G9B/5.026, G9B/11.008
International Classes:
G11B5/02; G11B11/10; G11C13/06; H04Q3/42
View Patent Images:
Foreign References:
DE873256C1953-04-13